Quaternary biocomposite of chitosan-polyvinyl alcohol/food grade algae/ montmorillonite clay for cationic methyl violet 2B dye removal: Optimization and desirability functions

Abstract

A quaternary composite adsorbent of chitosan-polyvinyl alcohol/food grade algae/ montmorillonite clay (CS-PVA/FGA/MMT) was synthesized by hydrothermal process to be a promising adsorbent for the removal of cationic methyl violet 2B dye (MV 2B). The adsorption working variables including CS-PVA/FGA/MMT dosage (A: 0.02–0.1 g/100 mL), pH of the dye solution (B: 4–10) and contact duration (C: 20–480 min) were optimized using response surface methodology with Box-Behnken design (RSM-BBD). The optimal conditions of the adsorption key parameters were confirmed by desirability function test and identified to be CS-PVA/FGA/MMT dosage of 0.099 g/100 mL and solution pH of 8. The equilibrium adsorption studies revealed that the adsorption of MV 2B dye on CS-PVA/FGA/MMT surface follows the Langmuir isotherm model and the pseudo-second-order kinetic model. The highest adsorption capacity of CS-PVA/FGA/MMT towards MV 2B was determined to be 105.7 mg/g at 25 ⁰C based on the Langmuir isotherm model parameters. The suggested mechanism of MV 2B adsorption by CS-PVA/FGA/MMT can be assigned to the various possible interactions such as electrostatic forces, n-π stacking, and H-bonding. This study shows that the synthesized CS-PVA/FGA/MMT material possesses a unique structure and preferable adsorption capabilities towards cationic dye. Therefore, it offers a practical solution for removing harmful cationic dyes from contaminated wastewater.